1. Field of the Invention
The present invention relates to a heat transfer system for and method of controlling a patient""s temperature. In another aspect, the present invention relates to a heat transfer blanket for and method of controlling a patient""s temperature. In even another aspect, the present invention relates to a heat transfer blanket for controlling a patient""s temperature where in the heat transfer blanket comprises independently controlled zones for heating and cooling, and a method for heating and cooling various parts of a patient at different temperatures and rates.
2. Description of the Related Art
Man is considered to be a tropical animal, with normal functioning requiring a body temperature of about 37xc2x0 C. Relying only upon that protection from temperature stress which is provided physiologically at birth, comfortable human survival would require an environment of 37xc2x0 C., +/xe2x88x92 perhaps 1xc2x0. See, xe2x80x9cHypothermia-physiology, Signs, Symptoms and Treatment Considerationsxe2x80x9d, Search and Rescue Society of British Columbia, compiled by Michael McEwan, 1995. The McEwan article further notes that a body can self-compensate for small upward or downward variations in temperature through the activation of a built-in thermal regulatory system, controlled by temperature sensors in the skin.
For example, the response to an upward variation in body temperature is the initiation of perspiration, which moves moisture from body tissues to the body surface, where evaporation causes cooling. Likewise, the response to a downward variation in body temperature is shivering, which is the body""s involuntary contraction and expansion of muscle tissue on a large scale in an attempt to generate heat.
Stiff and Sixta, xe2x80x9cHypothermia Care and Preventionxe2x80x9d, 1997, generally define hypothermia as occurring when the body""s core temperature drops below its normal 37xc2x0 C.
The McEwan article defines impending hypothermia as occurring when the core temperature decreases to 36xc2x0 C.
In the early stages mild hypothermia causes vigorous shivering which is usually accompanied by an increase in pulse and breathing rates. Cold, white hands and feet (as the blood vessels in the skin constrict) are the first signs of blood being shunted away from the body""s extremities.
The McEwan article describes mild hypothermia as occurring when the core temperature is dropped to the range of 34-35xc2x0 C. At this point, uncontrolled, intense shivering begins, although the victim is still alert and able to help self, however, movements become less coordinated and the coldness is creating some pain and discomfort.
The McEwan article defines moderate hypothermia as occurring when the core temperature is in the range of 31 to 33xc2x0 C. At this point shivering slows or stops, muscles begin to stiffen and mental confusion and apathy sets in. Speech becomes slow, vague and slurred with breathing becoming slower and shallower.
The McEwan article defines severe hypothermia as occurring when the core temperature is below 31xc2x0 C., with Stiff and Sixta defining severe hypothermia as resulting when the body temperature drops below 33xc2x0 C. Shunting of the blood continues, manifesting as bluish lips and finger tips from poor oxygenation of the tissues near the body surface. Decreased circulation as results in a build-up of acid metabolites (waste products) in the muscles of the extremities until shivering stops and is replaced by muscular rigidity. The pulse and respirations begin to slow as the body core cools to 30xc2x0 C. The heart may stop at temperatures of about 28xc2x0 C. or less.
Hypothermia can occur easily enough during any outdoor excursion, especially in wilderness situations where weather conditions may deteriorate unexpectedly or where travelers may become lost, injured or exhaust food supplies prematurely. Additionally, outdoor activities involving water presents the added possibility of emersion with the body cooling up to 25 times faster in water than in air.
Mild hypothermia is also a common occurrence during major surgery on the body. The usual causes of such perioperative hypothermia or anesthetic-induced impairment of thermal regulation, exposure to cold, altered distribution of body heat, and surgical exposure of the body cavity to a room temperature environment. This is particularly a problem in patients anesthetized for over two hours in where there are large incisions exposing the body""s interior to room temperature. Routine measures to reduce heat loss during operation include covering the skin, warming intravenous fluid and transfused blood, and increasing ambient temperature. In most operations, with the exception of those on the brain, prevention of hypothermia is a mainstay of anesthetic management because hypothermia during surgery can adversely affect the outcome. See xe2x80x9cColorectal Surgery Comes in From the Coldxe2x80x9d, The New England Journal of Medicine, Vol. 334, No. 19, Mortensen, et al, May 19, 1996.
As discussed above, hypothermia may be encountered as a result of an accident or may be inadvertently acquired during major surgery. In an odd twist, hypothermia may be induced by a physician in the treatment of various conditions usually those in which the physician desires to protect the brain or heart. For example, U.S. Pat. No. 5,486,204, issued Jan. 23, 1996 to Clifton discloses a method of treating a non-penetrating head wound with hypothermia. Such a treatment protocol includes specific defined times, temperatures, rates of change of temperature and the timing of the introduction of medications, and controlled rewarming. Additionally, hypothermia is frequently induced during surgery for intra cranial aneurysms.
The McEwan article notes that treatment of cold injuries has long been controversial. It is also clear that it is not enough merely to reheat a victim suffering from hypothermia, but that controlled heating must be applied. For example, Baron Larrey, Napoleon""s Chief Surgeon observed that those soldiers, suffering from hypothermia, who were placed closest to the campfire during Napoleon""s retreat from Russian died. These soldiers probably rewarmed rapidly. As a general principle initial management principles for treating hypothermia emphasized prevention of further heat loss, rewarming as soon as it is safely possible at a xe2x80x9csuccessfulxe2x80x9d rate (slowly) and rewarming the core before the shell in an attempt to avoid inducing lethal side effects during rewarming. This treatment goal is noted as being important, since hypothermia itself may not be fatal above 25xc2x0 C. core temperature. Fatalities at 25xc2x0 C. or greater normally occur during rewarming.
The McEwan article notices that hypothermia causes several reactions within the body as it tries to protect itself and retain its heat, the most important of these being vaso constriction, which halts blood flow to the extremities in order to conserve heat in the critical core area of the body. Shivering is noted as maintaining peripheral vaso constriction, which minimizes the severity of vascular collapse during rewarming. Induction of vasodilation in hypothermia patients may precipitate rewarming shock and metabolic acidosis. This may occur where the periphery (legs and arms) are warmed before the core (heart and lungs) are warmed. Furthermore, the rapid shunting of cold blood from the extremities to the core as a direct result of vasodilation may cause the core temperature to drop. Prevention of vasodilation is the reason why it is imperative that the hypothermia victim""s extremities not be rewarmed before the core. If vasodilation occurs, cold blood returning to the heart may be enough to put the patient into ventricular fibrillation. Again see, the McEwan article.
The McEwan article notes treatment for the different levels of hypothermia. According to McEwan, treatment for mild hypothermia includes keeping the head and neck covered. Stiff and Sixta note that treatment for mild hypothermia generally includes application of hot packs, water bottles, or warm campfire rocks wrapped in hot, wet towels to the groin, head, neck and sides of the chest. McEwan that treatment for moderate hypothermia includes keeping the head and neck covered, with mild heat applied to the head, neck, chest, armpits and groin of the hypothermia patient. For severe hypothermia, McEwan notes that treatment includes application of heat by skin to skin contact in the areas of the chest and neck with exhaled warm air or steam introduced near the patient""s nose and mouth. Stiff and Sixta note that treatment for severe hypothermia will include application of hot packs to the neck, armpits, sides of chest and groin of the hypothermia victim, with the head kept covered.
Air-warmed and cooled devices to maintain normothermia during surgery are available and in wide use. However, as many as 10% of patients are hypothermic during surgery despite use of these devices. Both air-warmed and existing fluid-warmed devices (see FIG. 1) suffer from the same limitations. They do not contact an adequate amount of body surface to either maintain normothermia during surgery for parts of the body other than the brain, or to safely induce hypothermia during brain surgery or after head injury. The current lack of devices to effectively control patient temperature results in poor clinical outcomes in many cases.
The following patents relate to various apparatus for applying heat or cooling to a patient.
U.S. Pat. No.2,093,834, issued Sep. 21, 1937 to Gaugler, discloses a refrigerating apparatus for use with a bed which generally includes a blanket having a plurality of ducts into which a cooling or heating medium is provided to either cool or heat a person lying in a bed.
U.S. Pat. No. 2,110,022, issued Mar. 1, 1938 to Kliesrath, discloses a bed cover in which a heating or cooling medium is circulated.
U.S. Pat. No. 2,512,559, issued Jun. 20, 1950 to Williams, discloses a pad or blanket or the like which is associated with a heat transfer unit for heating or cooling a person lying in a bed.
U.S. Pat. No. 2,938,356, issued May 31, 1960 to McMahon, discloses bedding in the form of sheets, blankets or mattresses, or a flying suit, which may be utilized to heat or cool an individual using the bedding or flying suit. The bedding or flying suit may be described as a flexible supporting material of low conductivity which has embedded in it two types of segments each type of which is at least semi-conductive. A direct current is passed through this material in such a manner that heat will be absorbed or given off at junctions depending upon the direction of the current.
U.S. Pat. No. 2,991,627, issued Jul. 11, 1961 to Suits, discloses a cooling and heating blanket which may be placed in close proximity to a human body. The cooling and heating blanket utilizes a plurality of Peltier junctions through which direct electrical current is passed to obtain heating or cooling. This Peltier effect may be enhanced by circulating air through the blanket in a flexible tube.
U.S. Pat. No. 3,112,792, issued Dec. 3, 1963 to Coleman, et al, discloses a personal thermal device which is essentially a full body suit through which a heat transfer fluid is circulated throughout. The design of the ""792 patent does not allow differential heating and cooling capability or exposed body parts for access for medical procedures.
U.S. Pat. No. 3,154,926, issued Nov. 3, 1964 to Hirschhorn, discloses, discloses a cooling blanket in which cold fluid is pumped through a plurality of rigid metal tubes.
U.S. Pat. No. 3,211,216, issued Oct. 12, 1965, to Coleman, et al, is a divisional of earlier described patent U.S. Pat. No. 3,112,792.
U.S. Pat. No. 4,094,357, issued Jun. 13, 1978, to Sgroi, discloses a heat transfer blanket having a plurality of flexible heat pipe sandwich between the outer most layers of the blanket.
U.S. Pat. No. 4,017,921, issued Apr. 19, 1977, to Hernandez, discloses a cooling blanket which utilizes a plurality of elongated chambers defined normally by a plurality of elongated joints between the blanket lamina, wherein the chambers are adapted for receiving ice.
U.S. Pat. No. 4,114,620, issued Sep. 19, 1978, to Moore, et al, discloses a patient treatment pad for hot or cold use which utilizes a pair of laminated plastic film panels defining a passage there between for circulating hot or cold water.
U.S. Pat. No. 4,118,946, issued Oct. 10, 1978, to Tubin, discloses a flexible sheet or garment to be worn on or around the human body, or body member for cooling, which flexible sheet or garment a viscous liquid heat transfer media in a first fluid path and a pressurized gas in a second fluid path to transfer heat away from the body. The ""946 device, however, is to be worn in situations of high external temperature and is not suited for medical applications where very precise control of the temperature of an injured or ill person who cannot auto regulate their own temperature is desired. Also, the ""946 devise""s rectangular shape that does not conform to the body.
U.S. Pat. No. 4,132,262, issued Jan. 2, 1979, to Wibell, discloses a heating and cooling blanket with heating means including a plurality of flexible elements positioned within the blanket for being electrically energized for supplying heat to the blanket, and cooling means including plurality of flexible fluid carrying conduits positioned within the blanket to which a heat transfer fluid can flow, such that the blanket may be retained below room temperature. These heating and cooling elements are provided in such a manner as to provide a thermal blanket having respective independently controllable zones, such that the zones may either concurrently heat and cool the user of the blanket. The ""262 invention discloses zones which may be independently heated and cooled. However, the zones of the ""262 device are rectangular zones in a rectangular blanket which neither conforms to the body nor provides access to the body for surgery or medical care.
U.S. Pat. No. 4,149,541, issued Apr. 17, 1979, to Gammons, et al, discloses a fluid circulating pad with interconnecting internal passages for circulating a hot or cold liquid for treating a patient.
U.S. Pat. No. 4,660,388, issued Apr. 28, 1987, to Greene, Jr., discloses a cooling cover comprising a plurality of small air jets through which air is directed onto the body of a user of the cooling cover.
U.S. Pat. No. 4,662,433, issued May 5, 1987, to Cahn, et al, discloses a cooling blanket which utilizes a stable circulating foam as the cooling medium.
U.S. Pat. No. 4,859,250, issued Aug. 22, 1989, to Buist, discloses a thermal electric heat pump or power source device which is provided with P-type and N-type elements made of either thin films or thick films for use on flexible or nonflexible substrates such as thermals, blankets or therapeutic devices for heating or cooling.
U.S. Pat. No. 5,014,695, issued May 14, 1991, to Benak, et al, discloses a cooling/warming jacket pad for the containment of physiological organs such as hearts and kidneys during medical procedures. The jacket of the ""695 patent, however, is designed to wrap around an organ inside the body.
U.S. Pat. No. 5,125,238, issued Jun. 30, 1992, to Ragan, et al, discloses a disposable patient heating or cooling blanket. The patient is bathed and conditioned air through a multiplicity of orifices in the bottom layers of the blanket and the size and location of the orifices are such that sufficient pressure exists within the blanket to prevent crimping blockage and to insure a uniform flow of air through the orifices throughout the blanket area.
U.S. Pat. No. 5,165,127, issued Nov. 24, 1992, to Nicholson, discloses a heating and cooling blanket apparatus which utilizes a circulating heat transfer fluid.
U.S. Pat. No. 5,265,599, issued Nov. 30, 1993, to Stephenson et al, discloses a patient temperature control blanket with controlled air distribution. The blanket is provided with a plurality of orifices through which controlled pressurized air is introduced upon the patient""s body to regulate patient body temperature.
U.S. Pat. No. 5,392,847, issued Feb. 28, 1995, to Stephenson, discloses a thermal medical blanket which distributes heated or cooling air upon the patient.
In 1992, one of the inventors utilized a modified non-commercial embodiment of the RotoRest bed (Kinetic Concepts, Inc.) in an hypothermia study. This bed had been equipped with cooling panels for wrapping the abdomen and chest. Unfortunately, this bed does not have the capability of warming and cooling different body surfaces at the same time, the cooling apparatus cannot be used independently of the bed, and the bed cannot be used in the operating room or post operative room because of limitations imposed on patient care by the RotoRest bed.
However, in spite of these advancements in the prior art, none of these prior art references disclose or suggest, an apparatus for selective rewarming of a hypothermia patient to rewarm various body parts at different rates and at different temperatures to minimize the occurrence of vasodilation. Additionally, none of these prior art references disclose a suit which wraps the torso and legs leaving the arms, buttocks, perineum and head exposed. Furthermore, none of the prior art references disclose panels which may be opened to gain access to the chest, abdomen, legs or backs to expose a surgical field or to provide access to these areas for necessary medical care.
For example, in the situation of a patient suffering from hypothermia or in whom hypothermia has been deliberately induced, exposure of the arms is necessary as they are the primary site for insertion of necessary intravenous lines. Exposure of the head is necessary to maintain control of the airway. The ability to gain ready access to the chest, back and abdomen (the core) is necessary should cardiopulmonary resuscitation be needed, to auscultate heart and breath sounds, to auscultate abdominal sounds or to provide exposure for surgeries of the chest, back or abdomen. Exposure of the legs is necessary for hygiene or for surgery of the legs. The perineum is always exposed in order to provide access at all time to the urinary tract and also because of the significant hygiene issues associated with these sites where body wastes are eliminated. Firm contact of the blanket to the torso and legs, however, is necessary to control temperature whether inducing hypothermia, maintaining hypothermia or rewarming. In a medical setting however, ready access to the torso and legs and exposure of head arms and perineum is required. None of the devises of the prior art meets these needs.
Thus, there is still a need in the art for apparatus for selective heating and cooling of various body parts of a human suffering from hypothermia so that various body parts can be heated and cooled at different rates and at different temperatures.
There is still another need in the art for an apparatus for heating and cooling of a patient in which the maximal body surface is in contact with the cooling/heating surface, which will also provide for easy access to the patient""s body for either surgery or routine patient care, while the patient is being heated and/or cooled.
These and other needs in the art will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.
It is an object of the present invention to provide for an apparatus for the selective heating and cooling of a patient so that various body parts can be heated and cooled at different rates and at different temperatures.
It is another object of the present invention to provide for an apparatus for the heating and cooling of a patient which also allows for easy access to various body parts of the patient during such heating and cooling.
These and other objects of the present invention will become apparent to those of skill in the art upon review of this specification, including its drawings and claims.
In one embodiment of the present application there is provided an apparatus for providing heating and cooling to a human body having a torso, legs, axillae, and ilia, with an axillary line defined as running between the axillae, and with an iliac line defined as running between the ilia. The apparatus includes at least one torso panel, suitable for wrapping the torso, defining cradles for receiving the axillae, where at least a portion of the torso panel extends above the axillary line and at least one fluid communication system providing fluid circulation within the torso panel.
In another embodiment of the present application there is provided an apparatus for providing heating and cooling to a human body having a torso, legs, axillae, and ilia, with an axillary line defined as running between the axillae, and with an iliac line defined as running between the ilia. The apparatus includes at least one torso panel suitable for wrapping the torso, where the torso panel defines curvilinear saddles for receiving the ilia, where at least a portion of the torso panel extends below the iliac line and a fluid communication system in fluid communication providing fluid circulation within the torso panel.
In even another embodiment of the present application there is provided an apparatus for providing heating and cooling to a human body having a torso, legs, axillae, and ilia, with an axillary line defined as running between the axillae, and with an iliac line defined as running between the ilia. The apparatus includes a first torso panel suitable for wrapping the torso, wherein the first torso panel defines cradles for receiving the axillae, where at least a portion of the first torso panel extends above the axillary line, a second torso panel suitable for wrapping the torso, wherein the second torso panel defines curvilinear saddles for receiving the ilia, where at least a portion of the second torso panel extends below the iliac line, and at least one fluid communication system in fluid communication with and providing fluid circulation within the first and second torso panels.
In even still another embodiment of the present application there is provided an apparatus for providing heating and cooling to a human body having a torso, the apparatus includes a panel having left and right outer edges, and positioned therebetween a left portion, a middle portion, and right portion, with both the left portion and the right portion further have a top and bottom portions, with the top and bottom portions of the left portion defining a left split running from the left outer edge to a left split point on the panel which defines a left edge of the middle portion, with the top and bottom portions of the right portion defining a right split running from the right outer edge to a right split point on the panel which defines a right edge of the middle portion, with the middle portion suitable for receiving at least a portion of the torso, and the upper and lower portions suitable for wrapping at least a portion of the torso.
In even still another embodiment of the present application there is provided an apparatus for providing heating and cooling to a human body having a leg comprising an upper leg, a knee, and a lower leg, the apparatus includes a panel including left and right outer edges, and positioned therebetween a left portion, a middle portion, and right portion, with both the left portion and the right portion further including upper leg and lower leg portions suitable from wrapping the upper leg and lower leg respectively, with the upper leg and lower leg portions of the left portion defining a knee opening running from the left outer edge to a left split point on the panel which defines a left edge of the middle portion, with the upper leg lower leg portions of the right portion defining a right split running from the right outer edge to a right split point on the panel which defines a right edge of the middle portion, wherein the middle portion is suitable for receiving at least a portion of the leg.